There is a photoacoustic apparatus that has been developed for breast cancer screening as a biological information acquisition apparatus of the related art that is described in Non Patent Citation. The biological information acquisition apparatus that is described in Non Patent Citation presses a subject (a breast) with a glass plate and an ultrasound probe, and irradiates the subject via the glass plate with illumination light (near-infrared light) that is emitted from a light source which is an Nd:YAG laser. Then, the biological information acquisition apparatus receives, with the probe, a photoacoustic wave that is an acoustic wave generated inside the subject, and generates and displays an image of tissue inside the subject, in particular, an image of breast cancer angiogenesis. An operation for image generation in such a manner is called image reconstruction. Note that a polymer with a thickness of 18.6 mm is provided on the surface of the probe. Because a sound velocity of a sound propagating through the polymer is different from a sound velocity of a sound propagating through the subject, the photoacoustic wave is refracted by the polymer before the photoacoustic wave is received by the probe. When refraction of the photoacoustic wave is not considered in image reconstruction, a reduction in resolution occurs.
A method for solving the above-mentioned issue is described in Patent Citation. In Patent Citation, a multifunction apparatus in which an X-ray mammography and an ultrasound apparatus are combined together is described. The X-ray mammography presses a subject using a compression plate that is used as a subject holding member, obtains information concerning X-rays by causing the X-rays to pass through the subject, and performs imaging in accordance with the information concerning X-rays. When the ultrasound apparatus is combined with the X-ray mammography, an ultrasound probe transmits/receives an ultrasound wave via the compression plate. FIG. 9 illustrates a state in which the ultrasound wave is refracted when the ultrasound wave enters the compression plate. Accordingly, referring to FIG. 9, delay times are calculated in accordance with Equations (101) to (104) so that refraction of the ultrasound wave which occurred due to the difference between the sound velocity in the compression plate and the sound velocity in the subject is corrected. Signals that are obtained by individual transformation elements are added to one another. T is an arrival time of the ultrasound wave. c1 and c2 are a sound velocity of a sound propagating through the compression plate and a sound velocity of a sound propagating through the subject, respectively. L1, L2, R1, R2, and D denote individual distances shown in FIG. 9. β1 and β2 are angles shown in FIG. 9. Note that Equation (104) is not clearly described in Patent Citation.
                    T        =                                            L              1                                      c              1                                +                                    L              2                                      c              2                                                          (        101        )                                          β          1                =                              sin                          -              1                                ⁡                      (                                                            c                  1                                                  c                  2                                            ⁢              sin              ⁢                                                          ⁢                              β                2                                      )                                              (        102        )                                T        =                                            R              1                                                      c                1                            ⁢              cos              ⁢                                                          ⁢                              β                1                                              +                                    R              2                                                      c                2                            ⁢              cos              ⁢                                                          ⁢                              β                                  2                  ⁢                                                                                                                                                (        103        )                                D        =                                            R              1                        ⁢                          tan              ⁡                              [                                                      sin                                          -                      1                                                        ⁡                                      (                                                                                            c                          1                                                                          c                          2                                                                    ⁢                      sin                      ⁢                                                                                          ⁢                                              β                        2                                                              )                                                  ]                                              +                                    R              2                        ⁢            tan            ⁢                                                  ⁢                          β              2                                                          (        104        )            